Fresh-cut fruit or minimally-processed fruit is a product that has recently appeared in markets. This fruit is subjected to a minimum processing which involves the washing, peeling, cutting, disinfection and packaging thereof in a passive or active modified atmosphere, to be finally stored under refrigeration conditions.
Fresh-cut fruit is a food product that is very susceptible to physical, chemical and biological alterations, which deteriorates at a higher rate than whole fruit. In fresh-cut fruit, respiration and metabolic processes are accelerated as a result of handling, for which reason it is essential to store the product in a modified atmosphere and keep it under refrigeration conditions.
Current regulations apply very strict microbiological criteria to fresh-cut fruit, in order to reduce to the minimum food toxi-infections or illnesses caused by the ingestion of fruit contaminated with bacteria such as Salmonella spp., Listeria spp. or Escherichia coli O157:H7 types.
Currently, in order to guarantee the safety of minimally-processed food products, treatments that involve washing the fruit with water with added sodium hypochlorite are usually applied. These treatments reduce the microbial load of the products, but have the disadvantage that they may leave a chlorine residue which facilitates the formation of substances that may be carcinogenic. Moreover, the treatment with hypochlorite does not prevent the growth of microorganisms during storage of the fruit or during the shelf life of the product.
The biocontrol of foodborne pathogenic bacteria in minimally processed products is a very desirable alternative to treatments with sodium hypochlorite. However, in order for this alternative to be viable, it is essential to find antagonistic microorganisms that are effective against any of the three aforementioned types of pathogenic bacteria (Salmonella spp., Listeria spp. and Escherichia coli O157:H7), both at room temperature and under refrigeration and modified atmosphere conditions. Moreover, it is desirable for these antagonists to be innocuous for both humans and vegetables, since, otherwise, they could harm the consumers or the treated product.
In the state of the art, antagonists have been disclosed for the biocontrol of foodborne pathogenic bacteria in fruit (“Biological control of postharvest decays of apple can prevent growth of Escherichia coli O157:H7 in apple wounds”, Janisiewicz, W. et al. JOURNAL OF FOOD PROTECTION 62 (12): 1372-1375. 1999, and “Biocontrol of the food-borne pathogens Listeria monocytogenes and Salmonella enterica serovar Poona on fresh-cut apples with naturally occurring bacterial and yeast antagonists”, Leverentz, B. et al. APPLIED AND ENVIRONMENTAL MICROBIOLOGY 72 (2): 1135-1140. 2006).
However, the antagonists used do not belong to the species Pseudomonas graminis and, moreover, none of them is effective against any of the microorganisms Salmonella spp. Listeria spp. and Escherichia coli O157:H7 either at room temperature or under refrigeration conditions.